David Cao

psql is the official command-line interface (CLI) for interacting with PostgreSQL databases. It’s lightweight, powerful, and essential for database administrators, developers, and DevOps engineers working with PostgreSQL. This guide covers everything from basic connection setup to advanced customization and troubleshooting—written…

PostgreSQL, as a powerful open-source relational database management system (RDBMS), places strong emphasis on security and granular permission control. Properly creating users and assigning appropriate permissions is fundamental to safeguarding database integrity and data security. This article provides a comprehensive,…

This guide walks you through the complete process of creating schemas and tables in PostgreSQL, including basic creation, associated usage, and permission configuration. We’ll follow industry best practices to help you avoid common pitfalls and manage database objects efficiently. First:…

In PostgreSQL, table access is not a single yes-or-no decision. A user might be able to: To accurately determine whether a user can access or manipulate a table, PostgreSQL provides multiple inspection layers—from high-level inquiry functions to raw system catalogs.…

In PostgreSQL, being able to authenticate as a user does not automatically mean you can connect to a database. Connection permission is a separate, explicit check—and if you’ve ever wondered why a valid user suddenly gets: FATAL: permission denied for…

PostgreSQL exposes object-level permissions through Access Control Lists (ACLs). While the SQL GRANT and REVOKE commands are familiar to most administrators, the internal ACL representation—especially when viewed through psql’s \dp command—can be confusing at first glance. One of the most…

PostgreSQL offers a sophisticated and layered security model that precisely controls how users authenticate and access data. To properly secure a PostgreSQL cluster, it is critical to understand the difference between two often-confused concepts: Although both are required for a…

If you’ve worked with PostgreSQL long enough, you’ve probably seen something like this: And the result looked like: At first glance, $user feels mysterious. Is it a variable? A placeholder? A real schema? Let’s unpack what $user actually means, how…